1. Field of the Invention
The present invention relates generally to asynchronous pull device for slide cover mechanism, and more particularly to a pull device for slide cover mechanism, which is able to provide stable driving force for the slide cover. With the synchronous pull device, the slide cover can be stably operated without deflection.
2. Description of the Related Art
Various slide cover structures have been developed and applied to different electronic devices to catch up the trend of product design and protect the panels of the electronic devices. For example, Taiwanese Patent Publication No. M392525 discloses a slide cover assembly and a slide cover electronic device. The slide cover assembly is disposed between the cover body and the main body of the electronic device. The slide cover assembly includes a support board connected with the cover body and a link board connected with the main body. A slide block is disposed in the support board. A torque spring assembly and an elastic member serve to apply a force to the slide block to slide the slide block. The slide block is connected with the link board via connection strings wound on locating poles of the support board. By means of the connection strings, the link board and the slide block always move relative to each other in reverse direct ions. The flat cable of the electronic device is conducted through the slide block and drivable by the slide block.
Taiwanese Patent Publication No. I280031 discloses a slide cover device including a substrate with a guide channel and slide rail. The guide channel is formed with a curved path having an overpass point. The slide cover device further includes an upper cover formed with elongated slots and inlaid in the slide rail. The slide cover device further includes elastic members positioned at the elongated slots. The elastic members include two springs and rolling members. The fixed ends of the springs are respectively fixed at the outer ends of the elongated slots. The rolling members are respectively connected with the free ends of the springs, which free ends extend in the elongated slots. When the upper cover is moved, the rolling members move along the guide channel to drivingly compress/decompress the springs. When the rolling members pass over the overpass point, the elastic members will pull the upper cover to automatically extend or retract the upper cover relative to the substrate.
Taiwanese Patent Publication No. I328088 discloses a slide module and a portable electronic device adopting the slide module. The slide module includes a fixed system and a movable system. A fixed frame is fixedly connected to the fixed system and a movable frame is fixedly connected to the movable system. Two reverse hook sections are disposed on two sides of the fixed frame. The lateral edges of the movable frame are fitted and received in the reverse hook sections, whereby the movable system can be moved relative to the fixed system between a first position and a second position. Linear torque springs are used to provide necessary driving force for the movable system.
In the above structure, coil springs or linear metal torque springs are used to provide necessary driving force for the slide cover. Such structure is practically applicable to small-size electronic products with small-volume and lightweight slide cover, such as cellular phones, handheld game machines and personal digital assistants (PDA). However, such structure can be hardly applied to a large-size electronic product such as a laptop computer or a tablet computer. This is because the movable system will have a heavier weight and it is necessary to move the movable system through a longer distance. When applying a push force to one single side of the movable system, the movable system is very likely to be biased. This will affect the smoothness of the sliding movement of the movable system. In some more serious cases, the movable system may be stuck with no possibility of moving. Moreover, it is hard to assemble the elastic members with the driven components. Also, elastic fatigue of the elastic members tends to take place after a period of use. This will lead to unsmooth operation of the slide cover.